This invention relates to handling molten metal. By molten metal, we mean a metal in a liquid form having a relatively high melting temperature such as 500.degree. F. or higher. Examples of such metals are aluminum and steel. More particularly, it relates to a flexible conduit for containing molten metal and a valve having a flexible conduit therein for controlling the flow of molten metal.
In the fabrication of metal, such as making mill products, for example, metal must be transported in molten form and sometimes the most convenient manner of transport is by flowing the metal via a trough or conduit. For example, in at least one method of making ingots for producing aluminum sheet or extrusions, molten aluminum is discharged through an opening in a melting furnace into a trough and thence to the molds. The mold is a relatively short hollow metal form having a cross section in the desired ingot shape extending downwardly from a level below the trough. The bottom of the form is closed with a member which is adapted for movement downwardly into a pit, and water spray nozzles are arrayed around the form. To make an ingot, molten metal is channeled into the top of the mold form as water is continuously sprayed on it. The metal solidifies as it cools and the movable member is moved steadily downwardly until the ingot is formed to the desired length. Typically, a number of ingots are made concurrently with the molten metal channeled from the trough to a plurality of molds. Since the ingots are continuously being lowered as they are formed, it is necessary that the flow of molten metal into the molds be maintained at a substantially uniform rate consistent with the rate of lowering. Furthermore, there is an optimum head of molten metal above the solidified ingot to be maintained in the mold to produce ingots free of defects. The head of molten metal affects the rate of solidification which, in turn, can affect the soundness of the ingot product. For a number of reasons, the rate of flow of metal entering the molds will vary if not controlled. For example, since the flow of metal from the furnace is by gravity through an opening near the bottom, the head of metal in the furnace affects the rate of discharge. As the furnace is drained, the head in the furnace lowers with a concurrent pressure drop on the metal flowing from the furnace.
Heretofore, the rate of flow of molten metal in molding metal has been controlled at the outlet from the furnace with the apparatus used to open and close the opening. Typically, the opening through the furnace wall is circular and is called a tap hole. The outlet end of the tap hole is frustoconical in cross section and a ceramic liner or seat fits within it. A tapered steel plug is driven into our out-of-tight contact with the ceramic seat to open or close the tap hole. In order to enable opening and closing the tap hole, the plug has a steel rod extending outwardly at an upward angle from its rear end. The rod rests on a bar placed across the trough leading from the tap hole. A lug extends upwardly from the rod, and to open or close the tap hole, an attendant simply hammers on the lug in one direction or another. Since the volume of metal issuing through the tap hole is a function of the clearance between the plug and the seat, the volume or rate of flow is also controlled by the attendant hammering on the lug. Although simple in operation, there are a number of problems associated with this system of flow control. For one thing, it is not a very precise way to control flow. Small changes in the plug position have a substantial effect on the metal flow. Further, the ceramic seats have to be replaced frequently because of erosion from the molten metal and damage during opening and closing, for example. In addition, dross and other foreign particles can become caught and stuck in the passage between the plug and seat and prevent adjusting downward or shutting off the flow without damaging the seat. From time to time, plugs freeze in the seats making their removal difficult.
For at least the foregoing reasons, it would be desirable to provide a valve for controlling the flow of molten metal.